Composition of polytetramethylene ether glycols and polyoxy alkylene polyether polyols having a low degree of unsaturation

ABSTRACT

Thus, there is provided according to the present invention polyol compositions comprising 
     (A) a polytetramethylene ether glycol, and 
     (B) a trifunctional active hydrogen compound-initiated polyoxyalkylene polyether polyol having a degree of unsaturation of not greater than 0.04 milliequivalents per gram of said polyether polyol.

FIELD OF THE INVENTION

This invention relates to blends of poly-tetramethylene polyetherglycols and polyoxyalkylene polyether polyols having a low degree ofunsaturation of 0.04 or less, and to the cast elastomers, spandexfibers, and thermoplastic polyurethanes made therefrom.

BACKGROUND OF THE INVENTION

Polyurethane elastomers often utilize one or more polytetramethyleneether glycols (PTMEG's) as a polyol component to react with one or morepolyisocyanates such as MDI because they can impart to the elastomer thehigh level of mechanical properties required for specific applications.PTMEG's are often used for such applications where high tensilestrength, low compression set, high resilience, and/or a high modulus ofelasticity are required. PTMEG's, however, can be difficult andexpensive to make due to the availability of starting materials and theformation of undesired side-reaction products during synthesis.

It would therefore be desirable to provide polyol compositions that canbe used to manufacture high-quality polyurethane elastomers whilereducing the amount of PTMEG required.

SUMMARY OF THE INVENTION

Thus, there is provided according to the present invention polyolcompositions comprising

(A) a polytetramethylene ether glycol, and

(B) a trifunctional active hydrogen compound-initiated polyoxyalkylenepolyether polyol having a degree of unsaturation of not greater than0.04 milliequivalents per gram of said polyether polyol.

The polyol compositions according to the present invention can be usedfor the manufacture of polyurethane elastomers via a one-shot techniqueor a prepolymer technique. Elastomers based on the polyol compositionsof the invention exhibit a good combination of properties such astensile strength, compression set, resilience, and/or a modulus ofelasticity, which often previously required the use pure PTMEG. Otherproperties, such as elongation and resilience, can often be improved byutilizing the blend compositions of the invention.

Thus, in one embodiment of the invention, there is provided a prepolymerobtained by reacting a polyol composition comprising at least theabove-described PTMEG and a polyoxyalkylene polyether polyol having adegree of unsaturation of 0.04 or less, with an organic polyisocyanate.The prepolymer may be isocyanate terminated by adding asub-stoichiometric amount of the polyol composition to the isocyanate,or hydroxyl terminated by adding to the isocyanate a molar excess of thepolyol composition.

In another embodiment of the invention, there is provided an elastomermade by reacting an organic di- or polyisocyanate with the polyolcomposition, optionally in the presence of a hydroxyl and/or aminefunctional chain extender at an equivalent NCO:OH ratio of at least1.5:1, where the polyol composition is made up of at least PTMEG and apolyoxyalkylene polyether polyol having a degree of unsaturation of 0.04or less. The polyol composition of the invention may be a principalpolyol component of the urethane elastomer-forming reaction mixture(i.e., one-shot method) or it may first be incorporated into aprepolymer prior to incorporation into the urethane elastomer-formingreaction (i.e., prepolymer methods).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

PTMEG's useful in the practice of the invention generally have a numberaverage molecular weight ranging from 500 to 5000, preferably 800 to3000, more preferably from 1000 to 2600. Techniques for the manufactureof PTMEG are well-known in the art, such as described in U.S. Pat. No.3,393,243, the disclosure of which is incorporated herein by referenceExamples of useful PTMEG's include POLYTHF® 650, POLYTHF® 1000, POLYTHF®2000, and POLYTHF® 2900.

PTMEG's are generally synthesized by a ring-opening chain extensionreaction of the monomeric tetrahydrofuran (THF). In one well-knownmethod, the ring-opening reaction is catalyzed by fluorosulfonic acid,followed by hydrolysis of sulfate ester groups and water extraction ofthe acid, followed by neutralization and drying. In many cases, thePTMEG will be solid at room temperature because of its high degree ofcrystallinity. In the event one desires to employ a room temperatureliquid PTMEG, the THF can be copolymerized with alkylene oxides (alsoknown as cyclic ethers or monoepoxides) as suggested in U.S. Pat. No.4,211,854, incorporated herein by reference. Such copolymers have anA-B-A block-heteric structure, wherein the A blocks are randomcopolymers of tetrahydrofuran and alkylene oxides, and the B block ismade up of polytetramethylene oxides.

The cyclic ethers copolymerizable with tetrahydrofuran are notparticularly limited, provided that they are cyclic ethers capable ofring-opening polymerization, and may include, for example, 3-memberedcyclic ethers, 4-membered cyclic ethers, cyclic ethers such astetrahydrofuran derivatives, and cyclic ethers such as 1,3-dioxolan,trioxane, etc. Examples of cyclic ethers include ethylene oxide,1,2-butene oxide, 1,2-hexene oxide, 1,2-tert-butyl ethylene oxide,cyclohexene oxide, 1,2-octene oxide, cyclohexylethylene oxide, styreneoxide, phenyl glycidyl ether, allyl glycidyl ether, 1,2-decene oxide,1,2-octadecene oxide, epichlorohydrin, epibromohydrin, epiiodohydrin,perfluoropropylene oxide, cyclopentene oxide, 1,2-pentene oxide,propylene oxide, isobutylene oxide, trimethyleneethylene oxide,tetramethyleneethylene oxide, styrene oxide, 1,1-diphenylethylene oxide,epifluorohydrin, epichlorohydrin, epibromohydrin, epiiodohydrin,1,1,1-trifluoro-2-propylene oxide, 1,1,1-trifluoro-2-methyl-2-propyleneoxide, 1,1,1-trichloro-2-methyl-3-bromo-2-propylene oxide,1,1,1-tribromo-2-butyleneoxide, 1,1,1-trifluoro-2-butyleneoxide,1,1,1-trichloro-2-butylene oxide, oxetane, 3-methyloxetane,3,3-dimethyloxetane, 3,3-diethyloxetane, 3,3-bis(chloromethyl)oxetane,3,3-bis(bromomethyl)oxetane, 3,3-bis(iodomethyl)oxetane,3,3-bis(fluoromethyl)oxetane, 2-methyltetrahydrofuran,3-methyltetrahydrofuran, 2-methyl-3-chloromethyltetrahydrofuran,3-ethyltetrahydrofuran, 3-isopropyltetrahydrofuran,2-isobutyltetrahydrofuran, 7-oxabicyclo(2,2,1)heptane, and the like.

The content of the copolymerized cyclic ether, if present, in a PTMEGmay be within the range of from 5 to 95% by weight, but when obtaining acopolymerized polyetherglycol containing oxytetramethylene groups as amain component which is effective as the soft segment in a polyurethaneelastomer such as spandex, the amount of the cyclic ether in the A blockcopolymerizable with THF is generally from 30 to 70 wt %. In the eventone chooses to randomly copolymerize cyclic ethers with THF across thewhole copolymer, the amount of cyclic ether may range from 5 to 60weight % of the copolymer.

Additionally, in the synthesizing reaction of PTMEG, a part of thestarting THF may be replaced with an oligomer of PTMEG as the startingmaterial. Further, in the synthesizing reaction of a copolymerizedpolyetherglycol, an oligomer of PTMEG or an oligomer of thepolyetherglycol to be synthesized may also be added as a part of thestarting material to carry out the reaction. In such a case, theoligomer generally has a molecular weight lower than the polymer to besynthesized. More specifically, one may use an oligomer having anumber-average molecular weight within the range of from 100 to 800 whensynthesizing a polymer with a number-average molecular weight of 1000 ormore, and an oligomer with a number-average molecular weight of 100 to2000 when synthesizing a polymer with a number-average molecular weightof 3000 or more. Also, an oligomer separated by fractional extraction orvacuum distillation from the PTMEG or the copolymerized polyetherglycolsynthesized may be employed. Such an oligomer may be added in an amountof up to 10% by weight into the starting monomer.

The degree of polymerization tends to decrease as the reactiontemperature is increased and therefore, and also in view of thepolymerization yield, the polymerization temperature should preferablybe -10° to 120° C., more preferably 30° to 80° C. If the temperatureexceeds 120° C., the yield decreases. The time required for the reactionis generally 0.5 to 20 hours, although it may vary depending upon thecatalyst amount and the reaction temperature. The reaction may becarried out in any system generally employed such as tank type or towertype vessel. It is also feasible by either batch or continuous system.

Catalysts used in the preparation of PTMEG are well known, and includeany cationic catalyst, such as strongly acidic cationic exchange resins,fuming sulfuric acids, and boron trifluorides.

The polyol blends of the present invention comprise a trifunctionalactive hydrogen compound-initiated polyoxyalkylene polyether polyol.Trifunctional active hydrogen compound-initiated polyoxyalkylenepolyether polyols useful in the practice of the invention should havenumber average molecular weights suitable for the particularapplication, and generally from 400 to 7000, preferably from 1000 to6500, more preferably from 1500 to 3500, and most preferably from 2000to 3000.

The hydroxyl numbers of the polyoxyalkylene polyether polyols used inthe invention correspond to the desired number average molecular weightby the formula:

    OH=(f) 56,100/equivalent weight

For most applications, suitable hydroxyl numbers for the polyoxyalkylenepolyether polyol ranges from 15 to 250, and most often from 25 to 120.

The polyoxyalkylene polyether polyols used in the invention have adegree of unsaturation of 0.04 meq KOH/g of polyol or less, preferably0.03 or less, more preferably 0.02 or less.

The structure of the polyoxyalkylene polyether polyol contains a nucleusof a trifunctional active hydrogen compound initiator compoundcontaining at least three hydrogen atoms reactive to alkylene oxides.Specifically, the reactive hydrogen atoms on the initiator compoundshould be sufficiently labile to open up the epoxide ring of ethyleneoxide. The initiator compound has a relatively low molecular weight,generally under 400, more preferably under 150.

Examples of initiator compounds useful in the practice of this inventioninclude, but are not limited to glycerin, trimethylol propane, and thelike. Another class of reactive hydrogen compounds that can be used arethe alkyl amines and alkylene polyamines having three reactive hydrogenatoms, such as ammonia, ethanolamine, diethanolamine, triethanolamine,isopropanolamine, diisopropanolamine, triisopropanolamine, and the like.It may be necessary to select catalysts or adjust reaction conditionsthat would allow both primary and secondary amine hydrogens to ring-openthe alkylene oxides in order to render diamines trifunctional.Conversely, it may be necessary to select catalysts or adjust reactionconditions to favor only primary amine hydrogens in order to rendertriamines trifunctional. Cyclic amines or amides may also be used asinitiators. A still further class of such reactive hydrogen compoundsare the polycarboxylic acids having the requisite number of functionalgroups. The initiator can also be one containing different functionalgroups having reactive hydrogen atoms, also, such as diethanolamine andthe like.

In one preferred embodiment, the polyoxyalkylene polyether polyols usedin the invention contain at least one hydrophobic block made frompropylene oxide or a mixture of propylene oxide and other cyclic ethers.Such other cyclic ethers are either of the type that are hydrophobicrelative to polyoxyethylene groups; or if of a hydrophilic character,are admixed with propylene oxide only in those relative amounts thatwill not render the polyol ineffective for its ultimate application. Thehydrophobic block may consist of a homoblock of oxypropylene groups or ablock of randomly distributed oxypropylene groups and other oxyalkylenegroups. As an alternative to or in combination with propylene oxide,butylene oxide may also be used, as it also exhibits hydrophobicproperties and yields polyols having a low degree of unsaturation.

The polyether of the invention may also be prepared by the additionreaction between a suitable initiator compound directly or indirectlywith a defined amount of propylene oxide to form an internal block ofoxypropylene groups, followed by further direct or indirect addition ofone or more other oxides.

The polyoxyalkylene polyether polyol may contain only ethylene oxidegroups, especially if the molecular weight is below 600. However, itpreferably contains from 50 to 100 wt. % of oxypropylene groups,preferably from 70 to 96 wt. % of oxypropylene groups, based on theweight of all of the cyclic ether groups added.

In one preferred embodiment of the invention, propylene oxide is addedto and reacted directly with the initiator compounds through thereactive hydrogen atom sites to form an internal block ofpolyoxypropylene groups. The structure of such an intermediate compoundcan be represented according to the following formula:

    R[(C.sub.3 H.sub.6 O).sub.w ].sub.3

wherein R is the nucleus of the initiator; w is an integer representingthe number of oxypropylene groups in the block such that the weight ofthe oxypropylene groups is from 50 to less than 100 weight percent, (or100 weight % if one desires to make a polyol based solely onoxypropylene groups and the initiator), based on the weight of allalkylene oxides added; and 3 represents the number of reactive sites onthe initiator molecule onto which are bonded the chains of oxypropylenegroups.

The polyether polyol may also comprise more than one internal block ofoxypropylene groups. By an internal block is meant that the block ofoxypropylene groups should be structurally located between the nucleusof the initiator compound and a different block of one or more differentkinds of oxyalkylene groups. It is within the scope of the invention tointerpose a block of different oxyalkylene groups between the initiatornucleus and the block of oxypropylene groups, especially if thedifferent oxyalkylene groups are also hydrophobic. In one preferedembodiment, however, the internal block of oxypropylene groups isdirectly attached to the nucleus of the initiator compound through itsreactive hydrogen sites.

The polyoxyalkylene polyether polyols used in the invention areterminated with isocyanate reactive hydrogens. The reactive hydrogensmay be in the form of primary or secondary hydroxyl groups, or primaryor secondary amine groups. In the manufacture of elastomers, it is oftendesirable to introduce isocyanate reactive groups which are morereactive than secondary hydroxyl groups. Primary hydroxyl groups can beintroduced onto the polyether polyol by reacting the growing polyetherpolymer with ethylene oxide. Therefore, in one preferred embodiment ofthe invention, the polyoxypropylene polyether polyol is terminated witha terminal block of oxyethylene groups. Alternatively, in anotherembodiment, the polyether polymer of the invention may be terminatedwith of a mixture of primary and secondary terminal hydroxyl groups whena mixture of ethylene oxide and, for example, propylene oxide isemployed in the manufacture of a terminal cap. Primary and secondaryamine groups can be introduced onto the polyether polymer by a reductiveamination process as described in U.S. Pat. No. 3,654,370, incorporatedherein by reference.

The weight of the terminal block of oxyethylene groups when employed, isat least 4 weight % to 30 weight %, preferably from 10 weight % to 25weight %, based upon the weight of all compounds added to the initiator.

The method of polymerizing the polyether polymers of the invention isnot limited and can occur by anionic, cationic, or coordinatemechanisms.

Methods of anionic polymerization are generally known in the art.Typically, an initiator molecule is reacted with an alkylene oxide inthe presence of a basic catalyst, such as an alkoxide or an alkali metalhydroxide. The reaction can be carried out under super atmosphericpressure and an aprotic solvent such as dimethylsulfoxide ortetrahydrofuran, or in bulk.

The type of catalyst used to manufacture the polyoxyalkylene polyetherpolyol is also not limited so long as the catalyst is of the type thatwill produce polyoxyalkylene polyether polyols having a degree ofunsaturation of 0.04 or less at the desired number average molecularweight. Suitable catalysts include the alkali metal compounds, alkaliearth compounds, ammonium, and double metal cyanide catalysts asdescribed in U.S. Pat. No. 3,829,505, incorporated herein by reference,as well as the hydroxides and alkoxides of lithium and rubidium. Otheruseful catalysts include the oxides, hydroxides, hydrated hydroxides,and the monohydroxide salts of barium or strontium.

Suitable alkali metal compounds include compounds that contain sodium,potassium, lithium, rubidium, and cesium. These compounds may be in theform of alkali metal, oxides, hydroxides, carbonates, salts of organicacids, alkoxides, bicarbonates, natural minerals, silicates, hydrates,etc. and mixtures thereof. Suitable alkali earth metal compounds andmixtures thereof include compounds which contain calcium, strontium,magnesium, beryllium, copper, zinc, titanium, zirconium, lead, arsenic,antimony, bismuth, molybdenum, tungsten, manganese, iron, nickel,cobalt, and barium. Suitable ammonium compounds include, but are notlimited to, compounds which contain ammonium radical, such as ammonia,amino compounds, e.g., urea, alkyl ureas, dicyanodiamide, melamine,guanidine, aminoguanidine; amines, e.g., aliphatic amines, aromaticamines; organic ammonium salts, e.g., ammonium carbonate, quaternaryammonium hydroxide, ammonium silicate, and mixtures thereof. Theammonium compounds may be mixed with the aforementioned basicsalt-forming compounds. Other typical anions may include the halide ionsof fluorine, chlorine, bromine, iodine, or nitrates, benzoates,acetates, sulfonates, and the like.

Of the alkali metals, cesium is the most preferred. Lithium, sodium, andpotassium are often not effective at reducing the degree of unsaturationof polyoxyalkylene polyether polyols at the higher equivalent weights.In a preferred embodiment, the polyoxyalkylene polyether polyols aremade with a cesium containing catalyst. Examples of cesium-containingcatalysts include cesium oxide, cesium acetate, cesium carbonate, cesiumalkoxides of the C₁ -C₈ lower alkanols, and cesium hydroxide. Thesecatalysts are effective at reducing the unsaturation of high equivalentweight polyols having a large amount of oxypropylene groups. Unlikedouble metal cyanide catalysts, which can also be effective at loweringthe degree of unsaturation of polyoxyalkylene polyether polyols, thecesium-based catalysts do not have to be removed from the reactionchamber prior to adding an ethylene oxide cap onto a polyether polyol.Thus, the manufacture of a polyoxypropylene polyether polyol having anethylene oxide cap can proceed throughout the whole reaction with acesium based catalyst.

The degree of unsaturation can be determined by reacting the polyetherpolymer with mercuric acetate and methanol in a methanolic solution torelease the acetoxymercuric methoxy compounds and acetic acids. Any leftover mercuric acetate is treated with sodium bromide to convert themercuric acetate to the bromide. Acetic acid in the solution can then betitrated with potassium hydroxide, and the degree of unsaturation can becalculated for a number of moles of acetic acid titrated. Morespecifically, 30 grams of the polyether polymer sample are weighed intoa sample flask, and 50 ml of reagent grade mercuric acetate is added toa sample flask and to a blank flask. The sample is stirred until thecontents are dissolved. The sample and blank flasks are left standingfor thirty (30) minutes with occasional swirling. Subsequently, 8 to 10grams of sodium bromide are added to each and stirred for two (2)minutes, after which one (1) ml of phenolphthalein indicates is added toeach and titrated with standard 1.0 N methanolic KOH to a pink endpoint.The degree of unsaturation is calculated and expressed asmilliequivalents per gram: ##EQU1## The acidity correction is made onlyif the acid number of the sample is greater than 0.04, in which case itis divided by 56.1 to give meq/g.

The reaction conditions can be set to those typically employed in themanufacture of polyoxyalkylene polyether polyols. Generally, from 0.005percent to about 5 percent, preferably from 0.005 to 2.0 percent, andmost preferably from 0.005 to 0.5 percent by weight of the catalystrelative to the polyether polymer is utilized.

Any catalyst left in the polyether polymers produced according to theinvention can be neutralized by any of the well-known processesdescribed in the art, such as by an acid, adsorption, water washing, orion exchange. Examples of acids used in the neutralization techniqueinclude solid and liquid organic acids, such as 2-ethylhexanoic acid andacetic acid. For ion exchange, phosphoric acid or sulfuric acid may beused. Extraction or adsorption techniques employ activated clay orsynthetic magnesium silicates. It is desirable to remove metal cationiccontents down to less than 500 ppm, preferably less than 100 ppm, mostpreferably from 0.1 to 5 ppm.

As for other processing conditions, the temperature at whichpolymerization of the polyether polymers occurs generally ranges from80° C. to 160° C., preferably from 95° C. to 115° C. The reaction can becarried out in a columnar reactor, a tube reactor, or batchwise in anautoclave. In the batch process, the reaction is carried out in a closedvessel under pressure which can be regulated by a pad of inert gas andthe feed of alkylene oxides into the reaction chamber. Generally, theoperating pressures produced by the addition of alkylene oxide rangefrom 10 to 50 psig. Generating a pressure over 100 psig increases therisk of a runaway reaction. The alkylene oxides can be fed into thereaction vessel as either a gas or a liquid. The contents of thereaction vessel are vigorously agitated to maintain a good dispersion ofthe catalyst and uniform reaction rates throughout the mass. The courseof polymerization can be controlled by consecutively metering in eachalkylene oxide until a desired amount has been added. Where a block of arandom or a statistical distribution of alkylene oxides are desired inthe polyether polymer, the alkylene oxides may be metered into thereaction vessel as mixtures. Agitation of the contents in the reactor atthe reaction temperature is continued until the pressure falls to a lowvalue. The final reaction product may then be cooled, neutralized asdesired, and removed.

The polyol composition of the invention may include additional polyolsin addition to the PTMEG and the above-described polyether polyol. Forexample, polyols of other functionalities, i.e., functionalities of 2 orof greater than 3, may be included. Such polyols may be prepared asdescribed above, except that an initiator having a functionality 2 orgreater than three is used, including polyols such as ethylene glycol,propylene glycol, diethylene glycol, dipropylene glycol, 2,3-butyleneglycol, 1,3-butylene glycol, 1,5-pentanediol, 1,6-hexanediol,pentaerythritol, sorbitol, sucrose and the like, and amines such asethylenediamine, toluenediamine, and the like. Polyols of differentfunctionalities may be incorporated either by physical blending of thefinished polyols or by including other functionality initiator(s) in amixture with the above-described difunctional initiator prior toreaction with alkylene oxide(s). Thus, a mixture of initiator compoundsmay be used to adjust the functionality of the initiator to a numberbetween whole numbers. If one desires to manufacture an elastomer havingonly a slight degree of crosslinking, a high proportion of an initiatorhaving a functionality of 2, to which is added relatively small amountsof tri- or higher functional initiator compounds, may be mixed togetherto arrive at an initiator having an average functionality close to 2 andup to 2.3. On the other hand, a larger proportion of tri- or higherfunctional initiator compounds can be mixed with a di-functionalinitiator compound when a higher degree of crosslinking is desired.

Other types of polyol may also be included in the polyol composition ofthe invention. For example, polyester polyols may be added to improvecertain mechanical properties of an elastomer such as tensile strengthand modulus of the urethane polymer. For some elastomeric applications,however, it is preferred to use only polyether polyols because they canbe more hydrolytically stable than polyester polyols, and they processwell due to their lower viscosities. Other polyols that can be employedin addition to the polyoxyalkylene polyether polymers of the inventionare hydroxyl terminated hydrocarbons, such as polybutadiene polyols,where a high degree of hydrophobicity is desired. Castor oils and othernatural oils may also be employed. In addition, polycaprolactones can beused to increase the tensile strengths of elastomers. Other polyetherpolyols may be added, and it is preferred that these polyether polyolshave a low degree of unsaturation to optimize the mechanical propertiesof the product.

Other ingredients in the polyol composition, besides the PTMEG and thepolyoxyalkylene polyether polyol, may include other polyols, chainextenders or curing agents, catalysts, fillers, pigments, uvstabilizers, and the like.

The above-described components of the polyol composition can be blendedtogether with standard mixing techniques, preferably in aPTMEG:polyether polyol weight ratio of from 20:80 to 95:5, althoughratios of greater than 95:5 may also be useful. If either of thecomponents (A) or (B) are solid, they should be liquified, preferably bymelting, prior to mixing. Preferably, the polyol composition of theinvention should form a homogeneous blend without visual phaseseparation. It may be necessary to adjust the relative molecular weightsof either or both of the components (A) and (B) in order to achieve ahomogeneous blend.

Depending upon the application of the elastomer, the average actualfunctionality of the blend should be from 2.1 to 2.8, preferably from2.2 to 2.6. In these embodiments, polyols having functionalities outsideof these ranges can be used so long as the average functionality fallswithin the range. In one embodiment that is preferred for certainapplications, the functionality of the blend should be maintained at 3.0or less to avoid losing too much elongation, a desirable feature forcertain elastomeric applications. In applications where high hardness,high tensile strength, and low elongations are desired, it may bedesirable for the actual average functionality of the blend to exceed3.0. For most elastomer applications, the mean number average molecularweight for the polyol composition of the invention can range from 500 to5000, preferably from 1000 to 4500, and more preferably from 1000 to2000.

One-component elastomers can be cured by moisture from the air.Two-component elastomers can be cured along with chain extenders withcompounds containing isocyanate reactive hydrogen. These chain extendersmay be contained in the polyol composition. Elastomers may be preparedusing the one-shot technique or the prepolymer technique. If theprepolymer technique is used, the polyol composition will usually befree of a chain extender during the manufacture of the prepolymer. Theprepolymer is then reacted with any remaining polyol composition whichat that point contains a chain extender. In the one-shot process, thepolyisocyanate is reacted at the outset with a polyol compositioncontaining the chain extender.

Chain extenders may be, and are typically, employed in the preparationof polyurethane elastomers. The term "chain extender" is used to mean arelatively low equivalent weight compound, usually less than about 250equivalent weight, preferably less than 100 equivalent weight, having aplurality of isocyanate-reactive hydrogen atoms. Chain-extending agentscan include water, hydrazine, primary and secondary aliphatic oraromatic diamines, amino alcohols, amino acids, hydroxy acids, glycols,or mixtures thereof. A preferred group of alcohol chain-extending agentsincludes water, ethylene glycol, 1,3-propanediol, 1,4-butanediol,1,10-decanediol, o,-m,-p-dihydroxycyclohexane, diethylene glycol,1,6-hexanediol, glycerine, trimethylol propane, 1,2,4-,1,3,5-trihydroxycyclohexane, and bis(2-hydroxyethyl) hydroquinone. Apreferred group of amine chain extenders includes1,3-diaminocyclohexane, piperazine, ethylenediamine, propylenediamine,and mixtures thereof.

Examples of secondary aromatic diamines include N,N'-dialkyl-substitutedaromatic diamines, which may be unsubstituted or substituted on thearomatic radical by alkyl radicals, having 1 to 20, preferably 1 to 4,carbon atoms in the N-alkyl radical, e.g., N,N'-diethyl-,N,N'-di-sec-pentyl-, N,N'-di-sec-hexyl-, N,N'-di-sec-decyl-, andN,N'-dicyclohexyl-p- and m-phenylenediamine, N,N'-dimethyl-,N,N'-diethyl-, N,N'-diisopropyl-, N,N,'-disec-butyl- andN,N'-dicyclohexyl-4,4'-diaminodiphenylmethane andN,N'-di-sec-butylbenzidine.

The amount of chain extender used may vary depending on the desiredphysical properties of the elastomer. A higher proportion of chainextender and isocyanate provides the elastomer with a larger number ofhard segments, resulting in an elastomer having greater stiffness andheat distortion temperature. Lower amounts of chain extender andisocyanate result in a more flexible elastomer. Generally, about 2 to70, preferably about 10 to 40, parts of the chain extender may be usedper 100 parts of polyether polymer and PTMEG and any other highermolecular weight isocyanate reactive components.

Catalysts may be employed to accelerate the reaction of the compoundscontaining hydroxyl groups with polyisocyanates. Examples of suitablecompounds are cure catalysts which also function to shorten tack time,promote green strength, and prevent shrinkage. Suitable cure catalystsinclude organometallic catalysts, preferably organotin catalysts,although it is possible to employ metals such as lead, titanium, copper,mercury, cobalt, nickel, iron, vanadium, antimony, and manganese.Suitable organometallic catalysts, exemplified here by tin as the metal,are represented by the formula:

    R.sub.n Sn[X--R.sup.1 --Y].sub.2,

wherein R is a C₁ -C₈ alkyl or aryl group, R¹ is a C₀ -C₁₈ methylenegroup optionally substituted or branched with a C₁ -C₄ alkyl group, Y ishydrogen or an hydroxyl group, preferably hydrogen, X is methylene, an--S--, an --SR² COO--, --SOOC--, an --O₃ S--, or an --OOC-- groupwherein R² is a C₁ -C₄ alkyl, n is 0 or 2, provided that R¹ is C₀ onlywhen X is a methylene group. Specific examples are tin (II) acetate, tin(II) octanoate, tin (II) ethylhexanoate and tin (II) laurate; anddialkyl (1-8C) tin (IV) salts of organic carboxylic acids having 1-32carbon atoms, preferably 1-20 carbon atoms, e.g., diethyltin diacetate,dibutyltin diacetate, dibutyltin diacetate, dibutyltin dilaurate,dibutyltin maleate, dihexyltin diacetate, and dioctyltin diacetate.Other suitable organotin catalysts are organotin alkoxides and mono orpolyalkyl (C₁ -C₈) tin (IV) salts of inorganic compounds such asbutyltin trichloride, dimethyl- and diethyl- and dibutyl- and dioctyl-and diphenyl- tin oxide, dibutyltin dibutoxide, di(2-ethylhexyl) tinoxide, and dibutyltin dichloride. Preferred, however, are tin catalystswith tin-sulfur bonds which are resistant to hydrolysis, such as dialkyl(C₁ -C₂₀) tin dimercaptides, including dimethyl-, dibutyl-, anddioctyl-tin dimercaptides.

Tertiary amines also promote urethane linkage formation, and includetriethylamine, 3-methoxypropyldimethylamine, triethylenediamine,tributylamine, dimethylbenzylamine, N-methyl-, N-ethyl- andN-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine,N,N,N',N'-tetramethylbutanediamine orN,N,N',N'-tetramethylhexanediamine, N,N,N'-trimethyl isopropylpropylenediamine, pentamethyldiethylenetriamine, tetramethyldiaminoethylether, bis(dimethylaminopropyl)urea, dimethylpiperazine,1-methyl-4-dimethylaminoethylpiperazine, 1,2-dimethylimidazole,1-azabicylo[3.3.0]octane and preferably 1,4-diazabicylo[2.2.2]octane,and alkanolamine compounds, such as triethanolamine,triisopropanolamine, N-methyl- and N-ethyldiethanolamine anddimethylethanolamine.

To prevent the entrainment of air bubbles in the sealants or elastomers,a batch mixture may be subjected to degassing at a reduced pressure oncethe ingredients are mixed together. In the degassing method, the mixedpolyurethane formed ingredients can be heated under vacuum to anelevated temperature to react out or volatilize residual water. Byheating to an elevated temperature, residual water reacts with theisocyanate to liberate carbon dioxide, which is drawn from the mixtureby the reduced pressure.

Alternatively, or in addition to the degassing procedure, thepolyurethane forming ingredients may be diluted with solvents to reducethe viscosity of the polyurethane forming mixture. Such solvents shouldbe nonreactive and include tetrahydrofuran, acetone, dimethylformamide,dimethylacetamide, normal methylpyrrolidone, methyl ethyl ketone, etc.The reduction in viscosity of polyurethane forming ingredients aid theirextrudability. For sealant applications, however, the amount of solventshould be kept as low as possible to avoid deteriorating their adhesionto substrates. Other solvents include xylene, ethyl acetate, toluene,and cellosolve acetate.

Plasticizers may also be included in the A- or B-side components tosoften the elastomer and decrease its brittleness temperature. Examplesof plasticizers include the dialkyl phthalates, dibutyl benzylphthalate, tricresyl phosphate, dialkyl adipates, and trioctylphosphate.

In addition to solvents or plasticizers, other ingredients such asadhesion promoters, fillers, and pigments, such as clay, silica, fumesilica, carbon black, talc, phthalocyanine blue or green, titaniumoxide, magnesium carbonate, calcium carbonate, UV-absorbers,antioxidants, and HALS may be added in amounts ranging from 0 to 75weight percent, based upon the weight of the polyurethane. Other fillersinclude dissolved gels, plasticells, graded and coated calciumcarbonate, urea solids, the reaction product of hydrogenated castor oilswith amines, and fibers.

The polyurethane elastomers of the invention can be prepared by theprepolymer technique or in a one-shot process. The elastomers of theinvention can be prepared by a reaction injection molding technique, orin a cast process wherein the polyurethane forming ingredients are mixedtogether and poured into a heated mold into pressure. Other techniquesinclude conventional hand-mixed techniques and low pressure or highpressure impingement machine mixing techniques followed by pouringpolyurethane forming ingredients into molds.

In a one-shot process, the PTMEG and the polyoxyalkylene polyetherpolyol of the invention, catalysts, and other isocyanate reactivecomponents forming the polyol composition (also known as "B-side"components) are simultaneously reacted with an organic isocyanate("A-side" components). Once the B-side components are mixed together,the urethane reaction commences; and the ingredients are poured orinjected into molds to make cast elastomers, or may be extruded or spunto make thermoplastic polyurethane or spandex fiber.

In a prepolymer technique, all or a portion of the PTMEG and thepolyoxyalkylene polyether polyol having an end group degree ofunsaturation of 0.04 or less, and any other isocyanate reactive polyolsin the polyol composition, and usually without any chain extender, arereacted with a stoichiometric excess of the organic isocyanate to forman isocyanate-terminated prepolymer. Such prepolymers usually have freeNCO contents of 0.5 to 30 weight %, and for many elastomericapplications, have free NCO contents of from 1 to 15 weight %. Theisocyanate-terminated prepolymer is then reacted as an A-side componentwith any remaining B-side components to form a polyurethane elastomer.In some cases, all of the B-side components are in the form of an activehydrogen-terminated prepolymer. In other cases, only a portion of thepolyol composition is reacted with the stoichiometric excess of organicisocyanate to form an isocyanate terminated prepolymer, which issubsequently reacted with the remainder of the polyol composition, as atwo-component elastomer. An isocyanate-terminated prepolymer is usuallyreacted with the isocyanate reactive functionalities in the polyolcomposition at an NCO to OH equivalent ratio of at least 1.5:1.

Alternatively, an active hydrogen-terminated prepolymer can be preparedif all or a portion of the PTMEG and the polyoxyalkylene polyetherpolyol having an end group degree of unsaturation of 0.04 or less, andany other isocyanate reactive polyols in the polyol composition, andusually without any chain extender, are reacted with a stoichiometricdeficiency of the organic isocyanate to form an activehydrogen-terminated prepolymer. The prepolymer is then reacted as aB-side component with A-side components to form a polyurethaneelastomer.

In one embodiment of the invention, there is manufacture of a spandexfiber using the blends of the invention. Spandex is, by definition, ahard-segment/soft-segment-containing, urethane-containing polymercomposed of at least 85% by weight of a segmented polyurethane(or urea).The term "segmented" refers to alternating soft and hard regions withinthe polymer structure.

Spandex is typically produced using one of four different processes:melt extrusion, reaction spinning, solution dry spinning, and solutionwet spinning. All processes involve differing practical applications ofbasically similar chemistry. In general, a block copolymer is preparedby reacting a diisocyanate with the polyol composition of the inventionin a molar ratio of about 1:2 and then chain extending the prepolymerwith a low molecular weight diol or diamine near stoichiometryequivalence. If the chain extension is carried out in a solvent, theresulting solution may be wet- or dry-spun into fiber. The prepolymermay be reaction-spun by extrusion into an aqueous or non-aqueous diaminebath to begin polymerization to form a fiber or the prepolymer may bechain extended with a diol in bulk and the resulting block copolymermelt-extruded in fiber form. Melt spinning is conducted in a mannersimilar to the melt extrusion of polyolefins. Reaction spinning istypically carried out after reacting the polyol composition with adiisocyanate to form a prepolymer. The prepolymer is then extruded intoa diamine bath where filament and polymer formation occursimultaneously, as described in more detail in U.S. Pat. No. 4,002,711.

In another embodiment of the invention, there is provided athermoplastic polyurethane (TPU) elastomer made with the blends of theinvention. TPU is made by reacting a plyol composition comprising PTMEGand a polyoxyalkylene polyether diol having a low degree of unsaturationwith an organic diisocyanate to form a linear polymer structure. Whileother polyols with higher functionalities than 2 can be combined withthe diol, these should be used in minor amounts if at all. It ispreferable that the functionality of the initiators used to make thepolyoxyalkylene polyether polyols is 2, and that no initiators havingfunctionalities of over or under 2 are used, in order to make thepolymer chain linear. The same type of chain extenders as describedabove can be used, with the preferable chain extenders being thedifunctional glycols.

The reaction may be carried out in a one shot process or by theprepolymer technique. In the one shot process, the raw ingredients arefed into the reaction zone of an extruder, heated at a temperatureeffective for polymerization to occur, extruded onto a conveyor belt,and pelletized. The prepolymer technique is similar except that theprepolymer and chain extender are the materials fed into the reactionzone of the extruder. The type of extruder employed is not limited. Forexample, either twin or single screw extruders can be used.

The following examples further describe the invention.

EXAMPLE 1

A polyol was prepared as an ethylene oxide(10%)/propylene oxide hetericadduct of glycerine having a 5 weight % terminal ethylene oxide cap, amolecular weight of 2854, and a hydroxyl number of 57.0, manufacturedusing cesium hydroxide as a polymerization catalyst, with a degree ofunsaturation of 0.012. This polyol was blended at various levels with2000 molecular weight PTMEG for use in the preparation of urethaneelastomers.

EXAMPLE 2

A weight of 200 g of a 3000 molecular weight glycerine-initiatedpolyoxypropylene polyether polyol having an OH number of 57.0 was mixedwith 5 g of antioxidants and 600 g of polytetramethylene ether glycolhaving a molecular weight of 2000. The mixture was stirred at 60° C. for2 hours in a nitrogen-blanketed vessel, and then allowed to cool to 40°C. A capped prepolymer was prepared by adding 175 g of methylenebis(4-phenylisocyanate) (MDI) to the polyol mixture and then heating theresulting mixture under vacuum to 90° C. for 3.5 hours. The resultingprepolymer was allowed to cool to 50° C., and spandex fibers were formedby extruding the prepolymer into a solvent bath containing 2.5% byweight of ethylene diamine viaconventional reaction spinning techniques.The spandex fibers of 840 denier (932 dtex) had the following physicalcharacteristics:

Second cycle unload power at 100% elongation: 0.016 g/dtex

Second cycle set: 28%

Break tenacity: 0.51 d/tex

The invention has been described in detail with reference to preferredembodiments thereof. It should be understood, however, that variationsand modifications can be made within the spirit and scope of theinvention.

What is claimed is:
 1. A polyol composition for use as a polyolcomponent to react with one or more polyisocyanates in the production ofa polyurethane elastomer consisting essentially of:(A)polyoxytetramethylene ether glycol, and (B) a trifunctional activehydrogen compound-initiated polyoxyalkylene polyether polyol having adegree of unsaturation of between 0.04 milliequivalents per gram and0.02 milliequivalents per gram of said polyether polyol, saidpolyoxyalkylene polyether polyol capped with oxyalkylene groups derivedfrom ethylene oxide in an amount of from 4 weight percent to 30 weightpercent based on the weight of all oxyalkylene groups.
 2. The polyolcomposition according to claim 1, wherein at least 33% of the hydroxylgroups on the polyol (B) are terminated with primary hydroxyl groups. 3.The polyol composition according to claim 2, wherein the number averagemolecular weight of the polyol composition is from 500 to
 5000. 4. Thepolyol composition according to claim 3, wherein the number averagemolecular weight of the polyol composition ranges from 1000 to
 4500. 5.The polyol composition according to claim 1, wherein the averagefunctionality of the polyol composition ranges from 2.1 to 2.8.
 6. Thepolyol composition according to claim 5, wherein the averagefunctionality of the polyol composition ranges from 2.2 to 2.6.
 7. Thepolyol composition according to claim 1, wherein said polyether polyolhas a degree of unsaturation of not greater than 0.03 milliequivalentsper gram of said polyether polyol.
 8. The polyol composition accordingto claim 1, wherein said polyether polyol has a degree of unsaturationof not greater than 0.02 milliequivalents per gram of said polyetherpolyol.
 9. The polyol composition according to claim 1, wherein theweight ratio of said glycol and said polyether polyol ranges from 99:1to 20:80.
 10. The polyol composition according to claim 9, wherein theweight ratio of said glycol to said polyether polyol ranges from 95:5 to40:60.
 11. The polyol composition according to claim 10, wherein theweight ratio of said glycol to said polyether polyol ranges from about90:10 to about 50:50, respectively.
 12. The polyol composition accordingto claim 1, wherein said polyether polyol is a triol prepared with acesium-containing catalyst.
 13. The polyol composition according toclaim 12 wherein said cesium-containing catalyst is cesium hydroxide.14. The polyol composition according to claim 1, wherein the glycol andpolyether polyol form a homogeneous mixture.
 15. A composition for useas a polyol component to reaction with one or more polyisocyanates inthe production of a polyurethane elastomer consisting essentially of:apolyoxytetramethylene ether glycol component in the amount of betweenabout 20 and 95 percent of the composition; and a trifunctional activehydrogen compound-initiated polyoxyalkylene polyether polyol componentin the amount of between about 80 and 5 percent of the composition, saidinitiated polyoxyalkylene polyether polyol having an average molecularweight of between 400 and 7,000, being capped with oxyalkylene groupsderived from ethylene oxide in an amount of from 4 weight percent to 30weight percent based on the weight of all oxyalkylene groups and adegree of unsaturation of between about 0.04 milliequivalents per gramand 0.02 milliequivalents per gram of said polyol.
 16. The compositionfor use as a polyol component of claim 15 wherein said initiatedpolyoxyalkylene polyether polyol has an average molecular weight ofbetween 1000 and
 6500. 17. The composition for use as a polyol componentof claim 15 wherein said initiated polyoxyalkylene polyether polyol hasan average molecular weight of between 2000 and
 3000. 18. Thecomposition for use as a polyol component of claim 15 wherein thecomposition has an average functionality of between about 2.1 and 2.8.19. The composition for use as a polyol component of claim 15 whereinthe composition has an average functionality of between about 2.2 and2.6.
 20. The composition for use as a polyol component of claim 15wherein said initiated polyoxyalkylene polyether polyol has a degree ofunsaturation of not greater than 0.03 milliequivalents per gram of saidpolyol.
 21. The composition for use as a polyol component of claim 15wherein said initiated polyoxyalkylene polyether polyol has a degree ofunsaturation of not greater than 0.02 milliequivalents per gram.